After the asteroid impact that ended the dinosaurs, Australia breaks away from the other southern continents and drifts alone across the ocean for tens of millions of years. Host Richard Smith follows the last 65 million years of that isolation, tracing how the continent's prehistoric jungles give way to eucalypt forests, grasslands, and deserts as the climate dries out. Mammals, birds, and grasses rise to dominance elsewhere in the world too, but Australia's version comes out strange: giant marsupials rule the land long after placental mammals have taken over other continents, and the Great Barrier Reef has not yet formed when humans first arrive. The film treats this as a story with three moving parts, climate, biology, and geology, each pushing the continent toward the ecosystem it has today. Smith travels the country to show where these changes are written into the landscape itself, from fossil beds to the reef's slow assembly. It closes NOVA's account of the continent's four-billion-year history by explaining why its wildlife looks like nowhere else on Earth.